The work here, in western France (Vendée), has mostly examined thermoregulation in amphibians, reptile and amphibian road mortalities and movements to and from winter dens in aspic vipers (Vipera aspis). The work on road mortalities is long term and the data are employed as proxies for long term population change. The study locality is a mixture of woodland, marshland, extensive monocultures and urban areas. The woodlands are frequently managed to harvest fuel and also for hunting activities. An important ecological feature is the summer drying of many aquatic areas, due to low rainfall between May and September. This affects species that are dependent on water, for instance - the frogs (Pelophylax sp) and semi-aquatic snakes (Natrix natrix and N. maura) that must migrate to new ponds.


Dense woodland with limited sunlight penetration often constrains thermoregulating reptiles to woodland edges particularly during cooler spring and autumn months. This use of 'edge habitat' requires a basking strategy that minimises detection by predators whilst at the same time enabling the uptake of solar energy. A frequently employed behaviour is 'mosaic basking' used by all the local snake species, probably in an attempt to avoid detection by raptors, especially buzzard (Buteo buteo).

viper snake france viper snake france
basking whip snake france


Roger Meek Herpetology All four common species of snake regularly bask along woodland edge -especially in spring where the most frequent sightings are of aspic viper. Gravid (pregnant) female vipers are more likely to bask in open locations. This is now known to concern offspring fitness since the closer the snake can attain optimal body temperatures the fitter the offspring it will produce. The cost is t basking in open locations which increases the risk of mortality from predators.

Below is an aspic viper from Xavier Bonnets laboratory at Chizé.



Foraging Snakes...

Foraging Snakes in France foraging snakes in France

Grass snakes Natrix natrix (above) operate as wide-ranging foragers when prey animals are scarce, which is often the case in mainly agricultural landscapes. In the search for food and mates grass snakes cover large distances, up to 500metres within 40 hectare home territories. This main food source is amphibians (mostly common toad Bufo bufo), although small rodents may be important in agricultural areas. Fish are usually too fast to be caught but dead or sick individuals may be consumed. When food is abundant they usually adopt a sit-and-wait hunting strategy, which consumes less energy but may also reduce the number of prey animals caught. The snake shown above was seen at a fishing pond south of the village of Chasnais, perhaps searching for green frogs that bask at the pond edge or for dead fish. Foraging snakes that frequently enter water may experience rapid cooling of body temperature to below optimum levels due to their high skin surface to body volume ratios. Body temperatures influence the speed a reptile can attain (Q 10  effects), which is critically important both for securing prey and escaping from predators and hence a period of basking is often required to return to optimum levels. The photographs illustrate this point, showing the grass snake foraging in a large fishing pond and then to elevate body temperature basking after reaching the waters edge.

Whip snakes Hierophis viridiflavus are large snakes (up to 2metres) that forage widely in search of food and mates. They operate at higher body temperatures than other snakes in the area (mean 31C compared to a mean of 28C in the N. natrix population studied by Adrian Hailey in Spain). This is likely an adaptation for hunting fast moving prey (lizards and small mammals). Whip snakes are habitat generalists, particularly favouring open and edge habitats to facilitate thermoregulation and movement. Radio tracked H. viridiflavus were found to operate from home sites that also served as winter hibernation dens. In Spring short movements lasting only a single day to reach basking sites are undertaken, followed by two-day exploratory trips that included foraging for prey. Longer excursions, which lasted for up to a month, covered distances up to 3km when secondary shelters were used for retreats.

The high activity levels of both species, particularly whip snakes, make them susceptible to roadkill. In addition, hatchling whip snakes (see photograph below)  frequently enter houses during dispersal from nest sites in late summer when they are often misidentified as vipers and killed. Domestic dogs kill adult snakes and juveniles by cats when they enter urban areas. Very large (2 metres) whip snakes have few natural predators. The buzzard (Buteo buteo) is an important predator but some failed predation attempts on very large snakes have been observed in Vendee.

Adult (left) and juvenile whip snakes differ in appearance. The transformation to adult pattern and colouration occurs when they reach their 5th year. Whip snakes will defend themselves by biting and although the bite is non-toxic, in adults it can draw blood.

Herpetology in France
Male whip snakes display ritualised combat during the spring breeding season in disputes over females; often a female is in the vicinity at the time. Injury to either animal is minimal or non-existant and simply a trial of strength. Male whip snakes are known to be able to follow both male and females by using pheromone trails and appear to be able to distinguish between the scents of males and females. This ability may have evolved in the absence  of large winter hibernation aggregations and the need to search for mates in spring. Other types of snake that hibernate together in large numbers, for instance, North American male garter snakes Thamnophis sirtalis parietalis, do not have the same selective pressures and are not capable of following conspecific males pheromone trails. Male-male trailing behaviour has only been observed in those species that have ritualised combat.

This pair of male H. viridiflavus were photographed in the Deux-Sèvres region of France in spring 2012.
whip snake france
whip snake france

The two photographs above of whip snakes found moving in urban areas in the villages of Lairoux (upper photograph) and Chasnais, in Vendee. At just over 1 metre in length both were adults and aged around 5years or more.  The snake above was in ecdysis (about to shed its skin) and hiding down a drain. A pdf of a paper describing anthropogenic sources of mortality in whip snakes in the Vendee can be found here (pdf 67). 

Viperine Snakes...
species in Marshlands of France
Reptiles in France

Viperine snakes, Natrix maura (above) are found around ponds, lakes and streams. Skin colour and pattern vary and some examples are shown here. This species is mainly a sentinel predator lying at the bottom of ponds in wait for passing fish or amphibians for periods up to 10 minutes at a time. None of the individuals caught have attempted to bite, usually releasing an unpleasant odour but some employ 'balling behaviour' - shown in the central photograph, where the head is at the centre of the 'ball'. The English herpetologist Adrian Hailey studied this species in Spain and found that around 20% of the snakes he captured employed the 'balling' tactic. Compared to N. natrix viperine snakes had less food in their stomachs, probably a consequence of differences in lifestyle (i.e. sentinel (N. maura) versus foraging (N. natrix)) but sentinel predators expend less energy capturing prey. Drying ponds and ditches during summer force N. maura to migrate to the remaining ponds that have water but it is at this time that many are killed on roads. Maturity is reached at between 3 and 5 years.

close up of a green lizard

green lizard in FranceHerpetology in France

green lizard in Vendee, Francep.muralis female

The green lizard (left) and wall lizard are the common lizard species. The green lizard (Lacerta bilineata) appears to mostly occupy woodland edge habitat including road verges and hedgerows. Wall lizards (Podarcis muralis) are more abundant around human habitations, even industrial areas. Recent research by Raoul Van Damme and his colleagues has demonstrated that green lizards are essentially sit-and-wait predators with the ability to accelerate rapidly and capable of reaching speeds in excess of 2.5metres per second. This optimises prey capture, but it is also important for escaping predators. Wall lizards, in contrast, more actively forage in dense vegetation and have slightly lower velocities (up to 2.13metres per second). Most lacertid lizards are sexually dimorphic with larger head size in males a distinguishing feature. Large heads are adaptive for male combat where territory is defended or in disputes over females. The green lizard in the top photograph has a relatively large head, and hence is male, whilst the smallish in the photograph second from top is female and below her the above male basking on soil substrate.. The photograph in the upper of the two wall lizard photographs is male, below it is a female. Females on the other hand have longer torsos, which enhances egg production. 

The photograph below shows a pair of green lizards in a hedgerow near the village of Chasnais. The larger head of the male (lower) can be clearly seen.  

pair of greenlizards in France


  • (2006). Body temperatures of the common toad, Bufo bufo, in the Vendee, France. Herpetological Bulletin 95, 21 – 24.pdf 54
  • (2008). Natural History Note; Natrix maura (viperine snake): defence behaviour. Herpetological Bulletin 104, 42 –43.pdf 59
  • (2009). Patterns of reptile road-kills in the Vendee region of western France. Herpetological Journal 19, 135 – 142.pdf 61
  • (2011). Natural History Note; Lacerta bilineata (western green lizard): field injury. Herpetological Bulletin 116, 40 - 41.pdf 63
  • (2011). Aspects of the thermal ecology of the European tree frog Hyla arborea in Western France. Bulletin de la Societe Herpetologique de France 138,1-11.pdf 64
  • (2012). Patterns of amphibian road-kills in the Vendee region of western France. Herpetological Journal 22, 49 - 56.pdf66
  • (2012). Anthropogenic sources of mortality in the western whip snake, Hierophis viridiflavus, in a fragmented landscape in Western France. Herpetological Bulletin 120, 4 - 8.pdf 67
  • (2012). Low survivorship in Rana dalmatina embryos during pond surface freezing. Herpetological Bulletin 120, 31 -33.pdf 68
  • (2012). Amphibians in Vendee; research summary. Froglog (July 2012) 20, 43 - 44. (IUCN Species Survival Commision).pdf 69
  • Non-technical articles on reptiles and amphibians can be found in 'The Deux-Sèvres Monthly' magazine. 'Snakes of Western France, The Whip Snake (Couleuvre verte et jaune)' and 'Frogs in France; the water or green frogs (des Grenouilles vertes)'



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